Reaming tool with radially extending blades

ABSTRACT

A downhole reaming tool is disclosed having radially extendible cutting blades extended by hydraulic pressure directed into the tool to force an inner tubular body having protrusions thereon with tapered sides forward against the walls of mating recesses defined in such radially extendible cutting blades to extend the blades.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention resides in the field of reaming tools for use in wells and the like and more particularly relates to a downhole reaming tool having radially extendible reaming members.

[0003] 2. History of the Prior Art

[0004] When drilling or working on bore holes for use, for example, in oil or gas exploration, it is common to drill such bore holes in a number of steps. First, a large surface hole is created and a casing is installed to act as a lining in the bore hole. Often, the next section of the bore is drilled using a smaller drill bit so that the second section of the bore hole has a smaller diameter than that of the first section. Subsequent sections of the bore holes are drilled using drill bits having progressively smaller diameters and lined with casings having similarly smaller diameters. It is often desired to increase the diameter of a section of the bore hole well below the surface. This operation is conducted using a tool often referred to as an underreamer.

[0005] Underreaming tools commonly comprise one or more pairs of cutting blades which are movable from a retracted position to an expanded position. For example, GB Patent No. 2,320,270 describes a tool in which a pair of blades is pivotally mounted on a tubular body. The extension of the blades can be controlled by a piston which is moved by an increase in fluid pressure in the tubular body. However, the pivot system used in the above arrangement is known to be unreliable as the degree of expansion of the blades is not easy to control. In addition, the extended blades only provide a short cutting region which is limited by the diameter of the tool.

[0006] An alternative mechanism was suggested in U.S. Pat. No. 4,842,082 which discloses a tool comprising a slidably movable ring. The slidably movable ring is urged against a second member by a spring, and cooperating tapered edges cause the slidable member to move in a radial direction. Thus, the diameter of the cutting blades is increased without the use of a pivot.

[0007] However, the above system has a number of drawbacks. Firstly, using a spring to provide the force to extend the cutting blades results in problems with control of the device. The spring provides a force that depends on the displacement from an equilibrium position and the spring constant. Thus, at a particular extension, the outward force has a particular value, which cannot be increased beyond the limitations of the spring. As a result, obstructions in the well may prevent extension of the blades. Furthermore, the properties of the spring will deteriorate over long periods of use, thereby decreasing the available force.

[0008] Secondly, in the device of U.S. Pat. No. 4,842,082, the cutting blades are prone to “cocking” which can occur when an unevenly tapered surface or an obstructing particle on one of the blade's edges can cause the sliding ring or cutting blade to stick, preventing further movement at the stuck edge. The other free-sliding edge will ride up its associated taper to a point where its radial extension is greater than that of the stuck edge, resulting in an angled cutting blade. In use, a cutting blade that is not parallel with the work string may cause unevenly cut well bores and/or helical grooves in the well.

SUMMARY OF THE INVENTION

[0009] It is an object of the present invention to provide a radially expandable downhole tool that includes an inner tubular body having at least one protrusion on an outer surface thereof, and a reaming member mounted on the inner tubular body having at least one recess on an inner surface thereof for receiving said protrusion(s), said recess(es) and said protrusion(s) being shaped such that relative axial motion between the reaming member and the tubular body causes a movement of the reaming member in a radial direction, such axial movement being actuated by hydraulic urging means.

[0010] In a preferred embodiment, the reaming member includes a reaming surface. The reaming surface can include a plurality of cutting blades spaced around the circumference of the inner tubular body. Each cutting blade can extend substantially the length of the inner tubular body and run parallel to the long axis of the inner tubular body. In a preferred embodiment the reaming member has a plurality of recesses, and the inner tubular body has a like number of protrusions. In one embodiment there can be two recesses and two protrusions. In a preferred embodiment the protrusions and recesses have mating sides which sides can be curved or tapered sides such as conically tapered or pyramidically tapered. The protrusions and recesses can be of the same length. The hydraulic urging means can be a piston actuable on the inner tubular body and operated by hydraulic fluid. The fluid can be pumped through a work string attached to the tool. Thus by varying the pump pressure of the hydraulic fluid the radial movement of the reaming member can be controlled.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1A illustrates a longitudinal cross-sectional view of the tool of this invention in an open position.

[0012]FIG. 1B illustrates a longitudinal cross-sectional view of the tool of FIG. 1 in an closed position.

[0013]FIG. 2a illustrates a cross-sectional view of a portion of the tool of FIG. 1A showing the interaction of the reaming member and the inner tubular body wherein the reaming member is extended.

[0014]FIG. 2b illustrates a view of a portion of the tool of FIGS. 1 and 1B showing the interaction of the reaming member and the inner tubular body wherein the reaming member is retracted.

[0015]FIG. 2c illustrates a cross-sectional view showing the inner tubular body and the reaming member in a retracted mode.

[0016]FIG. 2d illustrates a cross-sectional view showing the inner tubular body and the reaming member in an extended mode.

[0017]FIG. 3a illustrates a longitudinal view of a section showing the interaction of the reaming member and the inner tubular body in an alternate arrangement with the blade radially extended.

[0018]FIG. 3b illustrates a longitudinal view of a section showing the interaction of the reaming member and the inner tubular body in the alternate arrangement of FIG. 3 a with the blade retracted.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0019]FIGS. 1A and 1B illustrate a longitudinal cross-sectional view of tool 100 of this invention which tool includes reaming member 120 having a plurality of cutting blades such as cutting blades 121 and 122 running parallel to the longitudinal axis 175 of the tool and positioned around the circumference of the tool. Reaming member 120 is located on inner tubular body 130 which, in this embodiment, has a plurality of protrusions 131A, 131B, 132A and 132B. These protrusions are received by mating recesses 121A, 121B, 132A and 132B in cutting blades 121 and 122. Other blades can be provided such as seen in FIGS. 2c and 2 d. The tool has an outer tubular body 140 and hydraulic urging means in the form of mandrel 150. Mandrel 150 is movable within a cylinder formed by outer tubular body 140 and reaming member 120. Spring 170 is present between ledge 142 of outer tubular body 140 and head 152 of mandrel 150. The spring can be a compression spring, producing a force acting against downward movement of the mandrel. Mandrel 150 is in the form of a long tube consisting of upper section 150A and lower section 150B. The wall of the upper section has a greater thickness than that of the lower section, with a distinct step 151 in between the two sections. This step abuts edge 133 of inner tubular body 130 in this embodiment. The outer tubular body has a number of outlets 144 for the circulation of fluid. Additional outlets can be provided, positioned so that circulating fluid assists in the reaming action by cleaning debris from the cutting blades and/or lifting cuttings from the hole.

[0020] The tool is also fitted with a nose cutter 180. Nose cutter 180 can be a spade cutter with variable diameter as is conventional in the art.

[0021]FIGS. 2a-2 d illustrate more details of the inner tubular body and reaming member. The edges of the mating protrusions and recesses are tapered to allow, for example, cutting blade 122 and inner tubular body 130 to slide against one another, as seen in FIGS. 2a and 2 b. FIGS. 2c and 2 d illustrate cross-sections of the inner tubular body and reaming member showing cutting blades 121, 122, 123 and 124 which are shown retracted in FIG. 2c and extended in FIG. 2d.

[0022] In use, a work string, which is not shown, is attached to the tool and the tool is lowered into a well bore. The cutting blades are fully retracted, as seen in FIG. 1B, by virtue of spring 170 which urges mandrel 150 in an upward direction. Cutting blades 121 and 122 rest on inner tubular body 130 with protrusions 131A, 131B, 132A and 132B resting respectively inside recesses 121A, 121B, 122 a and 122 b which recesses are best seen in FIG. 1A. Thus the cutting blades shown in FIGS. 1B and 2b are in their retracted positions.

[0023] When the tool is in the desired region of the well bore, fluid is pumped into cavity 190 above mandrel head 152, increasing the fluid pressure in cavity 190 and the downward force on the mandrel head 152. This force is countered by spring 170 on the underside of mandrel head 152. However, when the compressive force of the fluid exceeds that of the spring force and the external inward force from the well bore, spring 170 is compressed. Mandrel 150, via step 151, pushes inner tubular body 130 in a downward direction. Cutting blades such as cutting blades 121 and 122 are attached to the tool so as only to have limited axial travel. Cutting blades such as cutting blades 121 and 122 are prevented from moving downward with inner tubular body 130, so the resulting force on cutting blades 121 and 122 from the downwardly moving tapered edges 161, 162, 163 and 164 of the inner tubular body causes cutting blades such as cutting blades 121 and 122 to be forced to ride up tapered edges 161, 162, 163 and 164 and be moved into a radially extended position, as shown in FIGS. 1A and 2a.

[0024] Once the cutting blades are radially extended, the tool can be rotated by a downhole motor, or by rotation of the whole work string for the reaming of the bore hole walls. The tool can be raised or lowered on the work string if required. The tool can be used, for example, to ream an inside surface of a bore hole or, for example, to remove scale, cement, barium or paraffin.

[0025] In order to retract the blades, the hydraulic pressure in cavity 190 is lowered by reducing the pump pressure. Mandrel 150 moves in an upward direction due to the force of spring 170, and inner tubular body 130 moves upwards by the force of spring 170, allowing the cutting blades such as cutting blades 121 and 122 to shift inward from outside pressure to their retracted positions.

[0026] The tool of this invention can be constructed in such a way that inner tubular body 130 is fixed to mandrel 150 so that the two move up and down together. Alternatively, when mandrel 150 is raised, inner tubular body 130 can return to its retracted position pushed by the cutting blades from external forces from the well bore. Thus pressure in the bore hole produces a force on the cutting blades which, via the tapered edges, forces inner tubular body 130 in an upward direction. If required, additional springs or biasing means can be provided to urge the cutting blades in an inward direction to ensure that they remain retracted when desired.

[0027] The edges of the protrusions of inner tubular body 130 and recesses in the blades must be shaped to allow smooth relative movement of inner tubular body 130 and reaming member 120. Any suitable curve can be used, but in one preferred embodiment the edges are tapered. The edges can be curved, pyramidically tapered or conically tapered. The angle of tapering chose depends on a variety of factors, including degree of travel (axially and radially), pressure used, required cutting force and friction present between the inner tubular body and the cutting blades. The angle of the blade taper can be in the range of 20 degrees to 60 degrees, and is typically 36.5 degrees.

[0028] Although the cutting blades are shown to have two recesses each, the invention is not limited to this arrangement or number of recesses. However, two or more recesses are preferable, because this arrangement provides a smoother movement and greatly decreases the likelihood of the tapered edges of the protrusions sticking, and the blade cocking as a result.

[0029] Although the cutting blades are shown as being straight and parallel to the longitudinal axis of the tool, in an alternate embodiment they can be profiled to clean no go profiles, valve profiles, sliding sleeves, nipples, seal bores or shifting profiles, as required. Typically the tool of this invention can be used for polishing rough edges in bore holes and for setting packers, casings or patches.

[0030] The edges of the cutting blades can be provided with a hardened facing, such as tungsten carbide. The tool can be used in both vertical and horizontal well bores.

[0031]FIG. 3a and 3 b shows the cutting blade 122 and inner tubular body 130 in an alternate embodiment. This embodiment is similar to the first embodiment except that the blades have protrusions and the inner tubular body has recesses. FIG. 3b shows inner tubular body 130 with the protrusions of cutting blades 121 and 122 resting within recesses in inner tubular body 130.

[0032] The tool can be run on coiled tubing, a work string, snubbing units or drilling rigs. When coiled tubing is used, the tool should be installed below the motor.

[0033] The present invention allows a greater degree of control over the extension and retraction of the cutting blades compared to tools of the prior art since the cutting blades' movement is controlled by fluid pressure. The pressure can be increased to exceed the combined effect of the spring bias and the external force on the cutting blades so that the blades can be radially extended more reliably. The blades can be retracted or extended as many times as needed by cycling the pump pressure.

[0034] Another important advantage of the present invention is that the blades can be fully retracted. Full retraction allows the tool to pass through seal bores of the completion components. In some embodiments the mandrel can engage the reaming member, forcing it to move over the inner tubular body, such body being fixed relative to the rest of the tool.

[0035] Although the present invention has been described with reference to particular embodiments, it will be apparent to those skilled in the art that variations and modifications can be substituted therefor without departing from the principles and spirit of the invention. 

I claim:
 1. A reaming tool having a longitudinal axis, said tool comprising: an inner tubular body; at least one protrusion disposed on said inner tubular body, said protrusion having tapered sides and a shape; at least one radially extendible cutting blade, said cutting blade having at least one recess defined therein for receipt of said protrusion, said recess having tapered walls and shape mating with the shape of said protrusion; means to move said inner tubular body forward; and means to retain said radially extendible cutting blade from moving forward while allowing said cutting blade to move radially outward forced by contact of said tapered protrusion against a side of said recess defined in said radially extendible cutting blade.
 2. The reaming tool of claim 1 further including: a plurality of cutting blades radially disposed around said inner tubular body.
 3. The reaming tool of claim 2 further including: at least two protrusions disposed on said inner tubular body, each having a tapered side; and at least two recesses defined in said cutting blades for receipt of said protrusions in mating relationship therewith.
 4. The reaming tool of claim 2 further including: a plurality of protrusions disposed on said inner tubular body, each having a tapered side; and a plurality of mating recesses defined in said cutting blades for receipt of said protrusions in mating relationship therewith.
 5. The reaming tool of claim 4 wherein said means to move said inner tubular body comprises a mandrel adapted for receipt of hydraulic pressure thereon, said mandrel engaged against said inner tubular body, said reaming tool further including a spring for returning said mandrel to an inactive position once said hydraulic pressure has been reduced below the compression level of said spring.
 6. The reaming tool of claim 5 wherein each protrusion on said inner tubular body is of a shape selected from the group consisting of curved, pyramidically tapered and conically tapered shapes and wherein the angle of tapering of the sides of the protrusion is between 20 degrees and 60 degrees. 